The invention relates to a plug-in and pull-out mechanism for an electrical switchgear apparatus being disconnected by an axial withdrawal motion. In particular, the invention teaches an extractable circuit breaker connection mechanism designed to be moved in translation between a plugged-in position a pulled-out position and an extracted position, with respect to a fixed external frame. The frame is shaped to form a housing and comprises an opening on the front face enabling the circuit breaker to be extracted and rear wall opposite the opening. The rear wall is equipped with connection modules each comprising a part for electrical connection, in particular, to an external busbar, and a second part called connection module, comprising one or more connection terminals, for electrical connection to the circuit breaker terminals.
Electrical connection between the connection terminals and the circuit breaker terminals is performed by means of plug-in contacts which conventionally comprise two fingers separated by a spacer. A flexible return means tends to urge the fingers against the spacer. The ends of the two fingers facing one another on a first side of the spacer together form a first pair of jaws for clamping a terminal of the circuit breaker and the ends of the two fingers facing one another on the other side of the spacer form a second pair of jaws for clamping an internal part of a connection terminal attached to the frame. The opening movement of one pair of jaws causes a closing movement of the other pair of jaws by a lever effect.
The two pairs of jaws do not have the same functions. A first stage of the assembly operation is in fact performed whereas the switchgear apparatus is in the extracted position, giving access both to its rear face and to the internal face of the rear wall of the external frame. In this position, the plug-in contact is fixed by one of its pairs of jaws, called fixing jaws, to the corresponding terminal, called fixing terminal, which is then freely accessible to the operator.
In a second stage, the circuit breaker is inserted in a cavity of the external frame shaped in the form of a housing, by an axial movement which generates a relative translational movement towards one another of the jaws which are still free, called the plug-in jaws, of the terminal facing them, called the plug-in terminal. It is the movement which is used to achieve proper plug-in. That is to say insertion of a protruding part of the plug-in terminal between the plug-in jaws, forces the latter to open. Due to the presence of the fixing terminal between the fixing jaws, the latter jaws cannot move any closer to one another. The contact point between each fixing jaw and the fixing terminal then fulfills the role of pivot for the corresponding arm and the separation movement of the plug-in jaws generates separation of the fingers at the level of the spacer against the force of the flexible return means. The flexible return means provide, in the plugged-in position, the force necessary for permanent contact between the plug-in jaws and the plug-in terminals. Inversely, when pull-out takes place, the extraction movement of the circuit breaker must generate separation of the plug-in jaws and of the corresponding terminal, and in no case, separation between the fixing jaws and the fixing terminal.
The present invention relates more particularly to fixing of the fixing jaws to the fixing terminal, i.e., to the terminal on which the plug-in contact has to remain when the electrical switchgear apparatus is pulled-out, a terminal which consequently comprises means which contribute to securing the plug-in contact on the terminal when pull-out takes place.
Conventionally, an auxiliary fixing element such as a bolt can be provided for this fixing. The bolt cooperates with a bore made in the body of the terminal and with a frame of the plug-in contact, as described in U.S. Pat. No. 4,160,142. This solution complicates assembly and disassembly operations. The plug-in contacts are however considered as wearing parts which are capable of being inspected regularly and replaced, if required. With this type of device, maintenance operations are therefore complicated. Finally, the presence of an auxiliary fixing part increases the number of parts, which gives rise to extra cost.
It has therefore been proposed to use the flexible return means of the plug-in contact to perform closing of the fixing jaws on the fixing terminal, as is described, for example, in the document FR-A-2,583,217. The flexible return means are springs borne by the plug-in contact and tend to return the two fingers to a middle position in which the two pairs of jaws are partially open. The operator acts on the end of the plug-in jaws to move the latter towards one another and to open the fixing jaws by lever effect which engages the fixing jaws on a protruding part of the fixing terminal. Fixing by latching is achieved by positive cooperation between a notch provided on one of the fixing jaws and a latching edge of conjugate shape provided at one end of the corresponding terminal. The invention relates to the latter type of fixing, for which the profile of the fixing terminal contributes to holding the plug-in contact on the terminal when pull-out takes place, by cooperation with the fixing jaws.
In the latter type of gripping, dimensioning of the plug-in contact has to meet several contradictory requirements. First, the force exerted by the spring on the jaws must be sufficient to enable gripping of the gripping jaws but sufficiently weak to enable the plug-in contact to be opened by the operator acting on the end of the plug-in jaws. Moreover, once the fixing jaws have been fitted on the corresponding terminal, the plug-in jaws are not perfectly aligned with the plug-in terminal. This alignment fault may result from gripping of the plug-in contact, from the manufacturing tolerances between the fixed frame, the circuit breaker and the system for guiding the latter in translation, or from wear of these parts.
To overcome this alignment problem, it has been proposed in the document FR-A-2,624,660 to shape the plug-in contact and fixing terminal in such a way that in the plugged-in position the plug-in contact can take an oblique position with respect to the fixing terminal. But, control of the movement requires numerous moving parts interacting between the plug-in contact and the fixing jaws. Fitting of the plug-in contact on the fixing terminal becomes complex and unfixing the plug-in contact from the fixing terminal requires the plug-in contact to be completely disassembled, which is not compatible with the ease of the maintenance requirement referred to above.
It therefore proves necessary to propose a simple and inexpensive latching device enabling, on the one hand, fixing and unfixing of the plug-in contact and of the gripping terminal by simple pressure on the end of the plug-in jaws, and which moreover enables pivoting of limited amplitude between the plug-in contact and the fixing terminal.